A new tool is being forged to treat advanced cancer tumours — the kind that are almost impossible to destroy using just chemotherapy and radiation.

Fifteen years ago Vuk Stambolic, a senior scientist with theOntario Cancer Institute at Princess Margaret Hospital, and his colleagues were studying the tumour-suppressing gene PTEN.

Without it, they discovered, cancer cells become “endlessly surviving.”

About half of all advanced cancer tumours either lack PTEN or have a defective version of the gene, says Stambolic. Nearly all cancers of the uterus and the endometrium are PTEN-deficient, as are about half of all breast cancers and prostate cancers.

A new study published in the latest issue of Science on which Stambolic is the principal investigator could change that.

It found that certain drugs make cells lacking PTEN vulnerable to chemotherapy and radiation — creating the potential for a new treatment combination that could tackle the most lethal cancers.

And it could reach cancer patients sooner rather than later.

“The agents that our research indicates would work in this scenario are already undergoing advanced clinical trials (in Toronto and around the world),” says Stambolic. “So it’s not like we’re inventing a new drug or anything . . . It’s the cocktail (of chemotherapy and the drugs) that has previously not been recognized as a tool for treatment.”

PTEN-deficiency is already easily determined through genetic testing as part of the movement toward personalized cancer care.

The approach, being studied extensively at Princess Margaret, builds a genetic profile of a cancer tumour and uses that information to match patients with treatment.

“We’re no longer thinking of cancers by site — breast cancer, prostate cancer, cancer of the lung. We’re molecular profiling, we’re thinking about a cancer that is defective in this number of genes. We’re starting to categorize cancer by their genetic information rather than the site of origin,” says Stambolic.

He hopes his research will help bridge the gap between just cataloguing that genetic information and using it to figure out the most effective therapies.

“This opens up a number of new doors for going after the cancers that are deficient in PTEN,” he says.